[feature] - Register a reporter

### Narrative

As an user
I want to register as a reporter with a social account
so that I can report an incident

### Acceptance Criteria

- **Scenario 1**:
Given an unregistered user
When they send a request for a new registration using a social account
And the social account is valid
And all registration fields are present
Then they should be registered successfully and logged in

- **Scenario 2**:
Given an unregistered user
When they send a request for a new registration using a social account
And the account is invalid
Then registration should fail

- **Scenario 3**:
Given an unregistered user
When they send a request for a new registration using a social account
And the registration fields are invalid
Then registration should fail

- **Scenario 4**:
Given a registered user
When they send a request for a new registration using their current social account
Then they should be logged in

No files, tests, or entry points are named. Start by locating the registration endpoint and the social-account authentication integration, then trace validation and login behavior for each acceptance scenario. Done means valid accounts register and log in, invalid accounts or fields fail, and existing users can log in with their current social account.

Written by the indexing model from the issue text.